But now some of the rebels fighting Assad say they have set up a mukhabarat of their own to "protect the revolution," monitor sensitive military sites and gather military information to help rebels plan attacks against government forces.

Amateur video posted on a social media website shows rebel forces in Syria taking over a military airport in Idlib, Syria. NBCNews.com's Dara Brown reports.

"We formally formed the unit in November. It provides all kind of information to (opposition) politicians and fighters. We are independent and just serve the revolution," said a rebel intelligence officer who goes under the name Haji.

Rebel commanders had put Reuters in touch with Haji, who is based in Syria, via Skype on condition he not be identified.

Haji said most of the rebel mukhabarat's members were army defectors and former intelligence officers, and that the information they gathered was distributed to all anti-Assad factions and rebel brigades without discrimination.

However, the organization appears to operate independently from the main opposition Syrian National Coalition and the Free Syrian Army, effectively answering to itself.

The new rebel body has operated secretly for months, Haji said, helping fighters carry out attacks on government targets. Haji declined to disclose details of the rebel agency, but said it operated across Syria, including in Aleppo and Idlib in the north, Deir al-Zor in the east and the capital Damascus, adding: "We have our spies among the regime who are providing us with information that we need, including military information."

Syrians have long exchanged horror stories of the dungeons of the intelligence branches where dissidents were incarcerated, often tortured and sometimes killed. Opposition activists insist their own mukhabarat will be nothing like those Assad inherited from his father, the late President Hafez al-Assad.

"The word security should mean the security of the people," said an opposition activist using the name Abu Hisham in Aleppo.

'Nothing will be ignored'In the Arab world's many past or present police states, Syria's mukhabarat has had a reputation as one of the most ruthless. It consists of at least five powerful agencies which spy on each other, tap phones of dissidents and vie for power.

Corruption, personal interests and a lack of communication among its branches might appear to offer avenues for rebels to infiltrate Assad's mukhabarat, but the security services are dominated by the Syrian leader's tight-knit Alawite minority.

The Alawites, who make up about 12 percent of Syria's 23 million people, have rallied behind Assad, fearing revenge by the mostly Sunni Muslim rebels if he is toppled.

Other minorities, which include Druze, Christians and Shiites, fear for their freedoms if the armed revolt brings Sunni Islamist hardliners to power.

Such fears deepened after documented abuses by some rebels accused of torturing and summarily executing their opponents, as well as of looting state and private property during nearly 22 months of conflict that has cost at least 60,000 lives.

Haji said his intelligence agents were documenting such violations so that the perpetrators could be held to account.

"We are watching everybody. We have gathered information about every violation that happened in the revolt," he said.

"Those we cannot punish now will be punished after toppling Assad. Nothing will be ignored. We have our members among all the working brigades. They are not known to be intelligence and they operate quietly."

His agents, Haji said, worked undercover as activists, citizen journalists or fighters.

While welcoming the formation of the rebel intelligence service, one insurgent commander voiced concern it might change its agenda to serve a group or a political party later on, just as Assad's mukhabarat had focused on protecting his rule.

"After toppling Assad all of this will be reshaped -- it is a temporary unit but there is fear that this unit will remain secretive the way it is now and starts executing unwanted agendas," said the commander, known as Obeida.

"We fear that later it will become political and serve a political agenda as if all our sacrifices never happened."